Force is any pull or push that can change the state of motion, shape, or direction of an object. Force can be classified into two types based on how it is exerted. Contact and non-contact forces. Non-contact forces are exerted on an object without any physical contact with it.

Non-contact force definition

A non-contact force is a force applied to an object without having any physical contact with the object. In other words, it is an action-at-a-distance force. There is always a distance between the two interacting bodies.

There is a general law on Earth, anything that goes up must come down. Why is it? Does anyone pull things down? No, it is the gravitational force of the Earth that pulls the object. The gravitational force requires no contact with the object. This is an example of a non-contact force.

Examples of non-contact force:

  • Earth pulling an apple hanging on a tree. There is actual contact between the ground and the apple, but still, it pulls it down toward it.
  • Magnet attracting iron nails towards it.
  • Charged balloons repelling each other at a distance.
  • Static charge on CRT television screens pulling your hair.

Types of non-contact forces

  • Gravitational
  • Magnetic force
  • Electrostatic force
  • Nuclear force.

Let us discuss each one of these forces in details with some examples.

Gravitational force

Gravitational force is a pulling force that is exerted between any two bodies with mass. Any object which has a mass in the universe will experience this force. That means we all are pulling each other. The computer screen might be attracting you with a gravitational force now. But, why are we not experiencing this force except that the Earth is pulling? It is because the gravitational force is proportional to the masses of the object and inversely proportional to the square of the distance.

Formula of the gravitational force between two objects:

formula of gravitational force
Formula of gravitational force

Where m1 and m2 are the mass of the two objects and r is the distance between them. G is the gravitational constant.

Examples of gravitational forces

  • Revolution of the moon around the Earth due to the gravitational force.
  • Revolution of the planets in our solar system around the sun. A gravitational force of 3.54×1022 N acts between them. You can read more here.
  • We are able to land back when we jump on the ground. This is the simplest example of a gravitational force.

Magnetic force

Magnetic force is the force exerted by magnetic materials on other magnets or on metal objects. Moving charged particles can also exert magnetic force Magnetic force can be a pull or push in nature. Tesla is the unit of magnetic force

Examples of magnetic forces

  • Working on a compass. The compass has a tiny magnet. The magnet gets repelled or attracted by Earth’s magnetic poles and hence shows the direction.
  • The attraction of iron nails to a magnet
  • Repulsion between like poles of two magnets.
  • The attraction between, unlike poles of a magnet.

Electrostatic forces

The electrostatic force is the force exerted between two charged objects. It can be attractive or repulsive in nature. Positive-positive or negative-negative repel each other and positive-negative charges attract each other. This is not very common in our day-to-day lives. You can read more here.

The formula of the electrostatic force between two charged objects:

formula of electrostatic force between two charges
Formula for electrostatic force

Where k is the coulombs constant. Q1 and Q2 are the magnitudes of charges and r is the distance between them.

Examples of electrostatic forces

  • Balloons attract each other after being rubbed.
  • The static change in front of television sets pulls your hair.
  • A lightning strike

Nuclear forces

Non-Contact Force
Image of a lithium atom. Neutrons(blue), protons(red) and electron(grey)
Image by Gerd Altmann from Pixabay 

All matter is composed of atoms, and each atom consists of electrons and a nucleus. The electrons are negatively charged and they revolve around the nucleus in orbits. The nuclear consists of positively charged particles called protons and neutral particles called neutrons. There is a force that is binding the neutron and protons together. This is called the nuclear force. And there is no contact between the particles. So, this is a type of noncontact force.

Application of nuclear forces

  • Widespread destruction can be caused due to the force of a nuclear bomb
  • The Sun undergoes continuous nuclear fusion and nuclear fusion reactions. So, nuclear energy is a source of the energy from the Sun.
  • Nuclear energy is also used to run power plants to generate electricity.

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